function Person (name, age) {
  this.name = name
  this.age = age
  this.greed = function () {
    console.log('Hello, I am ', this.name)
  }
}
Person.prototype.getInfo = function () {
  return this.name + ', ' + this.age
}
function Student () {}

Student.prototype = new Person('lee', 'can')

var st = new Student() // 
st.greed() // Hello, I am  lee



function Student2 (name, age) {
  Person.call(this, name, age)
}
var st2 = new Student2('b', 'bb')
console.log(st2.name) // b


function Student3 (name, age) {
  Person.call(this, name, age)
}
Student3.prototype = new Person()
var st3 = new Student3('c', 'cc')
console.log(st3.getInfo()) // c, cc